scholarly journals Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

2016 ◽  
Vol 17 (4) ◽  
pp. 309 ◽  
Author(s):  
D.A. Kazakov ◽  
V.V. Vol’khin ◽  
K. Kaczmarski ◽  
Yu.O. Gulenova ◽  
M.N. Obirina ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Fine Particles ◽  
Aqueous Media ◽  
Composite Catalyst ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Catalytically Active ◽  
Magnetite Particles ◽  
Magnetically Separable

<p>This paper deals with determining catalytic activities of titania (TiO<sub>2</sub>) with various crystalline structures and magnetite (Fe<sub>3</sub>O<sub>4</sub>) during mineralization of 4-nitrophenol in aqueous media by ozonation. Among the titania samples under study, amorphized TiO<sub>2</sub> was shown to have the highest catalytic activity, while magnetite was characterized by the lowest catalytic activity. A procedure is proposed to synthesize a magnetically separable composite (TiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub>) including amorphized titania and magnetite phases, which involves deposition of a catalytically active titania phase on preformed magnetite particles. We also studied the effect of mass ratio of titania and magnetite phases in the composite on its catalytic activity during 4-nitrophenol mineralization by ozonation. It was found that catalytic activity of composite increased as the amorphized titania phase was doped with magnetite phase up to 30% wt but as the magnetite portion in the composite catalyst was further increased, its activity decreased. According to Fourier transform infrared (FTIR) spectroscopy, content of catalytically active sites (hydroxyl groups of titania) in the composite catalyst decreases as compared to the pure phase of amorphized titania. Increase in catalytic activity of the composite as its magnetite content increases to 30% wt can be attributed to increase of accessibility of catalytically active sites (OH groups) for ozone, because specific surface area and total pore volume of the composite catalyst as determined by BET increase as compared to amorphized TiO<sub>2</sub> and catalytically active titania phase is located mostly on surface of magnetite particles which is indicated by scanning electron microscopy (SEM) results and electrophoretic light scattering (ELS) data. It was shown that the obtained composite catalyst of optimized composition, in spite of its fine particles, can be easily recovered from aqueous phase by magnetic field and used repeatedly in ozonation in order to promote water purification process.</p>

scholarly journals Effect of Li2O Doping on the Surface and Catalytic Properties of the Fe2O3–NiO/Al2O3 System

1998 ◽  
Vol 16 (1) ◽  
pp. 21-32 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
N.M. Deraz
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Mixed Oxide ◽  
Active Sites ◽  
Catalytic Properties ◽  
Surface Characteristics ◽  
Appreciable Change ◽  
Surface Areas ◽  
Catalytically Active ◽  
Specific Surface Areas

Ferric–nickel/aluminium mixed oxide solids have the formula Fe2O3–0.42NiO/Al2O3 were treated with Li2O (0.75–3 mol%) and heated in air for 4 h at 500°C and 800°C, respectively. The effects of this treatment on the surface characteristics of these solids and their catalytic properties in relation to CO oxidation by O2 have been investigated. The results reveal that Li2O doping at 0.75 mol% concentration resulted in an increase of 24% and 18%, respectively, in the value of the specific surface areas, SBET, of the solids precalcined at 500°C and 800°C, while the addition of 3 mol% Li2O led to a slight decrease of ca. 10% in the SBET value of the same solids. In contrast, irrespective of whether the doping process involved solids precalcined at 500°C or 800°C, a significant decrease of 37% and 78%, respectively, was observed in the catalytic activity of these materials. This decrease in catalytic activity was not accompanied by any appreciable change in the magnitude of the activation energy for the catalytic reaction, i.e. Li2O doping brings about a decrease in the concentration of catalytically active sites without changing their energetic nature.

Influence of preparation conditions on physicochemical properties and catalytic activity of stabilized zeolites

1980 ◽  
Vol 45 (7) ◽  
pp. 2042-2048
Author(s):  
Jana Nováková ◽  
Ludmila Kubelková ◽  
Blanka Wichterlová
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Structural Changes ◽  
Oh Groups ◽  
Stabilization Process ◽  
Preparation Conditions ◽  
Catalytically Active ◽  
Active Electron ◽  
Acid Centers ◽  
Stabilization Temperature

Highly decationized zeolite NH4NaY, stabilized by water vapour under steaming conditions at 1030 K, was characterized by its lattice constant, sorption capacity, quantity of extralattice Al, number and character of OH groups present after dehydration in vacuum at 670 K. The catalytic activity and the effect of Lewis and Broensted type acid centers were tested by oligomeration of ethylene and propylene at 310 K and isotopic exchanges of ethylene-d4 + OH and propylene-d6 + OH at 570 K. The properties of this zeolite were compared with zeolites stabilized under selfsteaming conditions at 1040 and 820 K. Structural changes caused by the stabilization process are more pronounced with the steamed zeolite than with the selfsteamed one; in the latter case they diminish with stabilization temperature. Accordingly, the results of catalytic measurements reveal the effect of strong Broensted acid centers in the case of low-temperature selfsteamed zeolite; these centers apparently originate from remainders of the original decationized zeolite. The high-temperature self-steamed zeolite is essentially inactive, whereas the activity of the high-temperature steamed zeolite suggest the presence of catalytically active electron-acceptor centers.

scholarly journals Effect of Na2O Doping on the Surface and Catalytic Properties of the Mn2O3/Al2O3 System

1995 ◽  
Vol 12 (2) ◽  
pp. 119-128 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
S. Hammad
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Catalytic Properties ◽  
Xrd Analysis ◽  
Manganese Carbonate ◽  
Oxidation Of Co ◽  
Mechanical Mixing ◽  
Catalytic Activities ◽  
Specific Catalytic Activity ◽  
Catalytically Active

Manganese/aluminium mixed oxide solids having the formula 0.2MnCO3/Al2O3 were prepared by mechanical mixing of a known weight of finely powdered manganese carbonate and aluminium hydroxide. The solids obtained were treated with NaNO3 (0.75–6 mol%) solution and dried at 110°C, then calcined in air at 500°C and 800°C for 6 h. The phases produced were identified by XRD analysis. The surface properties (SBET, Vp and r̄) of the pure and doped solids were studied by using N2 adsorption at – 196°C and their catalytic activities were determined by studying the oxidation of CO by O2at 125–300°C. The results obtained reveal that pure and doped mixed solids preheated in air at 500°C and 800°C consist of Mn2O3 (partridgite) and a poorly crystalline γ-alumina. Doping with sodium oxide at 500°C and 800°C resulted in a small decrease (14–19%) in the SBET value of the treated solids. However, this treatment brought about a significant modification in the catalytic activity of the doped solids. Doping with 0.75% Na2O at 500°C led to an increase of about 30–50% in the specific catalytic activity which was found to decrease on increasing the percentage of Na2O above this limit, falling to values smaller than that measured for the undoped catalyst. Doping at 800°C led to a progressive decrease in the activity of the treated solid to an extent proportional to the amount of dopant present. The doping process at 500°C and 800°C did not modify the mechanism of the catalytic reaction but altered the number of catalytically-active sites contributing in the catalysis of CO oxidation by O2 without changing their energetic nature.

scholarly journals Surface and Catalytic Properties of NiO and Fe2O3 Solids

1997 ◽  
Vol 15 (8) ◽  
pp. 593-607 ◽  
Author(s):  
A. Abd. El-Aal ◽  
A.M. Ghozza ◽  
G.A. El-Shobaky
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Active Sites ◽  
Pore Radius ◽  
Total Pore Volume ◽  
Surface Characteristics ◽  
Oxidation Of Co ◽  
Catalytic Activities ◽  
Catalytically Active ◽  
The Mean

The surface characteristics, viz., the specific surface area SBET, the total pore volume Vp and the mean pore radius r̄, of NiO and Fe2O3 were determined from N2 adsorption isotherms conducted at −196°C for the different adsorbents preheated in air at temperatures in the range 300–800°C. The catalytic activities exhibited in CO oxidation by O2 on the various solids were investigated at temperatures varying between 150°C and 400°C. The effect of heating the NiO and Fe2O3 solids in CO and O2 atmospheres at 175–275°C on their catalytic activities was also studied. The results showed that increasing the calcination temperature in the range 300–800°C resulted in a progressive decrease in the SBET value of NiO and Fe2O3. The computed values of the apparent activation energy for the sintering of the oxides were 71 and 92 kJ/mol, respectively. The sintering of NiO and Fe2O3 took place mainly via a particle adhesion mechanism. The catalytic activity of NiO decreased progressively on increasing its calcination temperature from 300°C to 800°C, due to a decrease in its SBET value and the progressive removal of excess O2 which was present as non-stoichiometric NiO. This treatment also decreased the catalytic activity of Fe2O3. The decrease was, however, more pronounced when the temperature increased from 300°C to 400°C which was a result of the crystallization of the ferric oxide into the α-Fe2O3 phase. An increase in the calcination temperature for both oxides from 300°C to 800°C did not modify the mechanism of oxidation of CO by O2 over the various solids but rather changed the concentration of catalytically active sites. Heating NiO and Fe2O3 in CO and O2 atmospheres at 175–275°C modified their catalytic activities, with Fe2O3 being influenced to a greater extent than NiO.

Preparation, Properties and Cytotoxicity Assessment of Nanosized Pt-Rh Composite Catalyst for the Decomposition of Gaseous Ammonia

2010 ◽  
Vol 160-162 ◽  
pp. 1285-1290
Author(s):  
Chang Mao Hung
Keyword(s):  
Catalytic Oxidation ◽  
Active Sites ◽  
Human Lung ◽  
Fixed Bed ◽  
Composite Catalyst ◽  
Gaseous Ammonia ◽  
Human Lung Cells ◽  
Selective Catalytic Oxidation ◽  
Catalytically Active

The behavior of the ammonia (NH3) oxidation was by selective catalytic oxidation (SCO) over a nanosized Pt-Rh composite catalyst in a tubular fixed-bed flow quartz reactor (TFBR) at temperatures between 423 and 673 K. The catalysts surface properties were characterized using UV-Vis and TEM. The experimental results show high activities for NH3 removal was achieved during catalytic oxidation over the Pt-Rh catalyst at 673 K with an oxygen content of 4%. N2 was the main product in the NH3-SCO process over the nanosized Pt-Rh composite catalyst. These results also verify that the Pt-Rh metals on catalyst surfaces, resulting in the formation of the remarkable catalytically active sites at the metal-support interface in the reduction of NH3 in this process. In addition, the nanosized Pt-Rh composite-induced cytotoxicity testing was mainly applied to the human lung MRC-5 cell line and the percentage of cell survival was determined by MTS analysis in vitro. For nanosized Pt-Rh composite, only minor cytotoxicity was observed when human lung cells were exposed.

scholarly journals Catalytically Active Imine-based Covalent Organic Frameworks for Detoxification of Nerve Agent Simulants in Aqueous Media

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 1974 ◽  
Author(s):  
Sergio Royuela ◽  
Rodrigo Gil-San Millán ◽  
María J. Mancheño ◽  
M. Mar Ramos ◽  
José L. Segura ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Functional Groups ◽  
Aqueous Media ◽  
Nerve Agents ◽  
Nerve Agent ◽  
Covalent Organic Frameworks ◽  
Preliminary Results ◽  
Catalytically Active ◽  
Nerve Gas

A series of imine-based covalent organic frameworks decorated in their cavities with different alkynyl, pyrrolidine, and N-methylpyrrolidine functional groups have been synthetized. These materials exhibit catalytic activity in aqueous media for the hydrolytic detoxification of nerve agents, as exemplified with nerve gas simulant diisopropylfluorophosphate (DIFP). These preliminary results suggest imine-based covalent organic frameworks (COFs) as promising materials for detoxification of highly toxic molecules.

scholarly journals Polymer Magnetically Separable Catalyst for Supercritical Deoxygenation of Fatty Acids

2019 ◽  
Vol 5 (11) ◽  
pp. 10-17
Author(s):  
A. Stepacheva ◽  
A. Semenova ◽  
N. Yablokova ◽  
E. Kupriyanova ◽  
D. Rud
Keyword(s):  
Fatty Acids ◽  
Catalytic Activity ◽  
High Specific Surface Area ◽  
Hypercrosslinked Polystyrene ◽  
Biodiesel Fuel ◽  
Polymeric Support ◽  
Ruthenium Oxides ◽  
Magnetically Separable Catalyst ◽  
Catalytically Active ◽  
Magnetically Separable

In this paper, the possibility of using a magnetically separated ruthenium-containing catalyst based on a polymer matrix of hypercrosslinked polystyrene in the supercritical deoxygenation of stearic acid to produce a second-generation biodiesel fuel is studied. The catalyst was synthesized by a successive deposition of iron and ruthenium oxides to the polymeric support. The resulting catalytically active Ru-Fe3O4-HPS system is characterized by high specific surface area (364 m2/g) and magnetization (4.5 emu/g). This catalyst allows obtaining a high (up to 86%) yield of hydrocarbons C17+ and exhibits high activity in the process of deoxygenation in supercritical n-hexane. It was found that the selected catalytic system retains its catalytic activity for at least 10 consecutive cycles.

scholarly journals Flexible and Responsive Nature of 2D Layered Conductive Metal-Organic Frameworks Determine Their Catalytic Activity in Oxidative Dehydrogenation of Propane

2020 ◽  
Author(s):  
Mohammad R. Momeni ◽  
Zeyu Zhang ◽  
Farnaz A. Shakib
Keyword(s):  
Electronic Structure ◽  
Catalytic Activity ◽  
Active Sites ◽  
Metal Organic Framework ◽  
Electronic Structure Calculations ◽  
Electronic Structure Methods ◽  
Catalytically Active ◽  
Metal Organic ◽  
Dynamics Simulations ◽  
Structure Calculations

A multi-faceted approach is introduced for investigating the effects of intrinsic and guest(water)-induced structural transformations/deformations and heterogeneity on catalytic activity of the 2D π-stacked layered Co3(HTTP)2, HTTP = hexathiotriphenylene, metal-organic framework. Through comprehensive molecular dynamics simulations coupled with periodic and cluster electronic structure calculations, we uncover a complex array of catalytically active sites in 2D Co3(HTTP)2 MOF which would have been entirely missed if conventional static electronic structure methods were to be employed.

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